Sound deadener



ll steel.

Patented Apr. 9, 1940 UNITED STATES I PATENT .OFFICE 2,190,615 SOUND nnanma Application February 4, 1938, Serial No. 188,638

1 Claim.

This invention relates to vehicle bodies such as automobiles, airplanes, trains, and other metallic structures subject to vibration, and has as its principal object to decrease the objectionable noises developed as a result of the vibration of such structures by brations therein.

I have discovered that by covering at least part of a metallic panel with thin sheet metal I 10 am able to decrease greatly the noise caused by the vibration thereof. Any kind of metallic sheet may be employed, though the softer metals like tin and lead appear to be less eflfective than the harder metals and alloys like brass, iron, and The thickness of the metal may be varied within wide limits, depending upon the amount of sound-deadening required and the emciency of the particular sound deadener used. Thus iron and aluminum .015 inch thick gave excellent results. Tin plate, which is iron thinly coated with was found to be anexcellent sound deadener when applied in the form of plates .006 in. thick. Tin foil .003 in. thick had some effect as a sound deadener when cemented to a freely vibrating panel, but was decidedly inferior to thicker tin plates and to thin plates of harder metals.

The invention may be better understood by referring to the accompanying drawing in which:

Fig. 1 is a side elevation of an automobile body, partly broken away.

P18. 2 is an elevation of an automobile door showing a preferred embodiment of the invention.

Fig. 3 is a section on line 3-3 of Fig. 2.

Fig. 4 is an elevation of an automobile door partly broken away'showing a modified form of the invention, and

Fig. 5 is a view similar to that in Fig. 4 showing a further embodiment of the invention.

Referring to the drawing, the automobile body II is lined on the inside with a thin metallic sheet ii applied by any desired means. It is unnecessary to adhere the sheet to the body over the entire surface. Thus the tin plate i2 was spot-welded to the automobile door it at sufficient points to hold the sheet in contact with the body. The sheets may also be applied by cementing with rubber cement over the entire contact area, clamping at the edges, spot-weld ing at the edges, or cementing at the edges. When test panels were covered with a tin plate .008 in. thick by all of the above methods, and the panels were caused to vibrate, it was found that the metallic sheet applied by any of these quickly dampening the vimethods was such a good sound deadener that individual differences could not be detected.

Although for the best results the metallic panels should be entirely covered with the thin metallic plate, covering part of the surface has been found to have beneficial effects. In one modification the panel I was covered with evenly spaced metal strips I! one inch wide adhered thereto by rubber cement it. The relationship between the area covered and the sound deadening efficiency was roughly series of tests in which a panel 20 x 20 inches in area was covered with .008 in. tin plate by cementing with rubber cement over the entire contact area, and other similar panels were partly a covered with tin plate by the same method. The ratings given below are the number of seconds before the noise emitted by the panel ceased when the panel was suspended and struck with a hard rubber mallet.

i s: of ba are tin plate 8 3? Gwmmc moment vibration eased Complete coverage l Centered-parallel to two edges... 5 Evegly spaced in one direction--- 18 4..-... 0

Eight strips evenly spaced in one 8 direction-(our strips evenly spaced per en olor.

It will be readily seen that many other modifications may be evolved whereby the desired results are obtained by covering only parts of the structure. It is also within the scope of this invention to use sheets with openings therein as sound deadeners, as, for instance, a strip of iron plate 1 excellent materials. .Other fibers such as those obtained from old rubber tires may also be used. In one modification, the panel II was covered with a fibrous sheet i8 and thin tin plate I! which was spot-welded to the panel. This condetermlned by a struction dampened any vibrations in the panel in a veryv short space of time. The fibrous sheet material may be either plain, or embossed to produce irregular surfaces such as a wattle or dialent materials and varying the dispositions of the materials with respect to each other and to the vehicle body may be made without departing from the spirit of the invention as defined in the appended claim.

I claim: v

Means for damping vibrations in a substantially flat panel of a sheet metal structure, said means comprising a separate sheet of metal which is much thinner thanthe metal of the panel and is in direct contact with a major portion of the surface of the panel, and is fastened to the panel only at widely-spaced intervals.

' LEONARD C. SURPRENANT. 

